Patent GB-804922-A (GB)
Title: Improvements in or relating to axial-flow fluid machines for example compressors andturbines
Inventor: HAWORTH LIONEL
IPC: F01D9/04
Filed: 1956-01-13
Abstract: 804,922. Axial-flow turbines and compressors. ROLLS-ROYCE Ltd. Dec. 28, 1956 [Jan. 13, 1956], No. 1315/56. Class 110 (3). In a multi-stage axial-flow fluid machine such as a compressor or turbine of a gas turbine engine, the stator blades of each row are provided at their radially outer ends with platforms which form part of the wall of the working field annulus, each platform being supported from the stator casing, and the platforms of adjacent rows of stator blades have aligned axial extensions which together afford an annular stator shroud encircling the tips of the row of rotor blades between the adjacent rows of stator blades. The axial extensions of the platforms are offset radially from the radially inner surfaces of the platforms so as to provide a channel into which the integral tip shrouds of the rotor blades extend. In the gas turbine shown, the rotor comprises three rows of blades 10, 11, 12 mounted at the peripheries of rotor discs. The stator casing 13 supports three rows of stator blades 14, 15, 16 each stator blade being provided at its radially outer end with a platform 14b, 15b, 16b. The platforms 14b of the first row of stator blades are provided with extensions 19 which together with upstream extensions 23 on the platforms 15b of the secondstage stator blades 15 form an annular shroud around the tip shrouds 24a of the intermediate row of rotor blades 10. The extensions 19, 23 are offset radially outwardly of the platforms 14b, 15b so as to afford a channel in which the rotor blade tip shrouds 24a are received. The extensions 19 are provided with radial surfaces 24 which co-operate with radial surfaces 25 formed on the rotor blade tip shrouds 24a so as to provide a gas seal. The extensions 19 of the platforms 14b are also formed with radial flanges 20 which engage in a circumferential channel 18 formed in the annular rib 17 on the inner surface of the casing 13, the guide vanes 14 being located in the axial direction thereby. The guide vanes 14 are located in the circumferential direction by means of radial pegs 21 mounted in the casing and engaging recesses in bosses 22 on the platforms 14b. The platforms 15b of the stator blades 15 are provided with hooked portions 27, 28 which engage in grooves 31, 32 formed in the ribs 17, 35 formed in the casing 13 and dogs 39 on the platforms 15b engage with dogs 38 provided on the ribs 17, 35 to locate the platforms circumferentially. The platforms 15b are located axially by means of rings 40, 41 which extend between the ribs 35, 36 and abut radial extensions 42 on the downstream extensions 43 of the platforms 15b. The blade platforms 16b are located radially and circumferentially by means of hook portions and dogs similarly to the platforms 15b of the blades 15. The platforms 16b are located axially by means of a ring 50 abutting flanges 30a at the downstream ends of the platforms 16b. The extensions 43 on the platforms 15b and extensions 44 on the platforms 16b co-operate to provide a shroud around the tips 24a of the rotor blades 11 and a gas seal is provided similarly to that at the tips of the rotor blades 10. Passages are provided for flow of cooling air in the ribs 17, 35, 36 and in the ring 40. Specification 623,508 is referred to.